Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$184.29	5.143%	$193.768	$193.77	$193.75	$193.80
Purchase #2	$96.29	4.715%	$100.8301	$100.83	$100.85	$100.80
Purchase #3	$52.65	6.674%	$56.1639	$56.16	$56.15	$56.20
Purchase #4	$172.86	9.774%	$189.7553	$189.76	$189.75	$189.80
Purchase #5	$241.63	10.859%	$267.8686	$267.87	$267.85	$267.90
Purchase #6	$53.70	12.331%	$60.3217	$60.32	$60.30	$60.30
Purchase #7	$249.31	10.236%	$274.8294	$274.83	$274.85	$274.80
7 purchase totals =	$1,050.73		$1,143.5370	$1,143.54	$1,143.50	$1,143.60